Detecting device, detecting method, and recording medium

ABSTRACT

A light source ( 11 ) of a disguising mask detecting device ( 1 ) emits light at a person who is a subject. A camera ( 12 ) acquires images in multiple different wavelength ranges of reflected light of the light emitted at the person. A face detector ( 172 ) detects a face region of the person from the images acquired by the camera ( 12 ). A determiner ( 173 ) determines that the person is wearing a disguising mask when luminances of the face region in the images satisfy specific relations different from relations exhibited by skin.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 17/503,439 filed on Oct. 18, 2921, which is acontinuation application of U.S. patent application Ser. No. 15/124,500filed on Sep. 8, 2016, which issued as U.S. Pat. No. 11,188,770, whichis a National Stage Entry of international applicationPCT/JP2014/056756, filed Mar. 13, 2014, the disclosures of all of whichare incorporated in their entirety by reference herein.

TECHNICAL FIELD

The present disclosure relates to a detecting device, detecting method,and non-transitory recording medium.

BACKGROUND ART

Face authentication techniques for analyzing face images captured by acamera and authenticating the individual (simply termed faceauthentication hereafter) are known. A problem with such faceauthentication is unjust authentication in which someone elseimpersonates an individual by using a photograph of the individual.Moreover, various techniques for preventing unjust authentication due toimpersonation are known.

For example, Patent Literature 1 describes a technique ofthree-dimensional detection using multiple face images for preventingunjust authentication due to impersonation using photographs or thelike.

CITATION LIST Patent Literature

-   Patent Literature 1: Unexamined Japanese Patent Application Kokai    Publication No. 2012-069133.

SUMMARY OF INVENTION Technical Problem

However, if someone disguises himself as an individual by wearing asophisticated disguising mask, the figure is three-dimensional and theabove three-dimensional detection technique fails to prevent unjustauthentication.

Moreover, with recent sophisticated disguising masks, even the human eyesometimes fails to judge whether a disguising mask is worn. For example,at an airport immigration, a person wearing a disguising mask may clearvisual matching by an immigration officer by using a forged passportwith a photograph of the disguising mask.

In addition to the above case of a disguising mask, similar disguise canbe made by using something to disguise that is difficult to visuallyjudge (for example, a sheet of something resembling skin in appearance).In view of such a circumstance, a technique for detecting things todisguise that are difficult to visually judge with high accuracy isdemanded.

The present disclosure is made with the view of the above situation andan objective of the disclosure is to provide a detecting device,detecting method, and non-transitory recording medium for detectingthings to disguise with high accuracy.

Solution to Problem

In order to achieve the above objective, the detecting device accordingto a first exemplary aspect of the present disclosure comprises:

-   -   an image acquirer acquiring images in multiple different        wavelength ranges of reflected light of light emitted at a        person; and    -   a determiner determining whether luminances of a face region in        the images acquired by the image acquirer satisfy specific        relations different from relations exhibited by skin.

In order to achieve the above objective, the detecting method accordingto a second exemplary aspect of the present disclosure comprises:

-   -   an image acquisition step of acquiring images in multiple        different wavelength ranges of reflected light of light emitted        at a person; and    -   a determination step of determining whether luminances of a face        region in the images acquired in the image acquisition step        satisfy specific relations different from relations exhibited by        skin.

In order to achieve the above objective, the non-transitory recordingmedium according to a third exemplary aspect of the present disclosuresaves a program that allows a computer to function as:

-   -   a determiner determining whether luminances of a face region in        images of a person captured in multiple different wavelength        ranges satisfy specific relations different from relations        exhibited by skin.

Advantageous Effects of Invention

The present disclosure makes it possible to detect things resemblingskin in appearance with high accuracy.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graphical representation showing the spectra of luminancesof reflected light when light is emitted at human skin and silicone;

FIG. 2 is a block diagram showing the configuration of the disguisingmask detecting device in embodiments;

FIG. 3 is a diagram showing the structure of the camera in theembodiments;

FIG. 4A is an illustration showing an exemplary visible light image;

FIG. 4B is an illustration showing regions in the visible light imageshown in FIG. 4A;

FIG. 5 is a flowchart showing an exemplary process flow of the maskdetection procedure;

FIG. 6 is a flowchart showing an exemplary process flow of the maskdetermination procedure in Embodiment 1;

FIG. 7 is a flowchart showing an exemplary process flow of the maskdetermination procedure in Embodiment 2;

FIG. 8 is a flowchart showing an exemplary process flow of the maskdetermination procedure in Embodiment 3; and

FIG. 9 is a block diagram showing another exemplary configuration of thedisguising mask detecting device 1 shown in FIG. 2 .

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detailhereafter with reference to the drawings.

Embodiment 1

A disguising mask detecting device 1 according to Embodiment 1 of thepresent disclosure is installed, for example, near an entry gate in anairport immigration area. The disguising mask detecting device 1 has thefunction of determining whether a person who intends to pass through theentry gate wears a disguising mask and when he wears a disguising mask,giving notice accordingly.

Here, the disguising mask detected by the disguising mask detectingdevice 1 is a sophisticated mask like those used in special effectsmakeup for a young actor to play a role of an old man in movies and madeof thin silicone resembling human skin in appearance. Therefore, it isdifficult for a human to visually judge whether such a disguising maskis worn.

First, the principle of disguising mask detection by the disguising maskdetecting device 1 will be described. FIG. 1 is a graphical presentationshowing the spectra of luminances of reflected light when light isemitted at objects. In this figure, the dotted line presents thespectrum of reflected light of light emitted at human skin. On the otherhand, the solid line presents the spectrum of reflected light of lightemitted at silicone. Here, the luminance indicates the degree ofbrightness.

In this figure, the luminance of reflected light of light emitted atsilicone abruptly falls in a wavelength range around 1140 nm to 1220 nmmarked by hatched lines, which is an infrared wavelength band, and isobviously different from the luminance of reflected light of lightemitted at human skin. Here, an abrupt fall occurs because the siliconeabsorbs light in the wavelength range marked by the hatched lines welland weakens the reflected light.

The disguising mask detecting device 1 utilizes the above difference inspectrum of luminance of reflected light between silicone and humanskin, and detects a disguising mask depending on whether an abrupt falloccurs in the wavelength range marked by the hatched lines.

Subsequently, the configuration of the disguising mask detecting device1 will be described. The disguising mask detecting device 1 comprises,as shown in FIG. 2 , a light source 11, a camera 12, a speaker 13, aliquid crystal monitor 14, an operator 15, an external storage 16, and acontroller 17.

The light source 11 is a halogen light source, is turned on/off based oninstructions from the controller 17, and emits light at a person who isa subject. Here, the light source 11 may be a strobe or argon bulb.However, a halogen light source includes a lot of constituents in theinfrared wavelength band and therefore is suitable for use as thehalogen light source 11.

Reflected light of the light emitted at a person by the light source 11enters the camera 12. The camera 12 captures images of the reflectedlight in the visible light range, in a wavelength range of 1166±5 nm, ina wavelength range of 1190±5 nm, and in a wavelength range of 1214±5 nmall at once at the same time under the control of the controller 17. Inthe following explanation, the image in the visible light range capturedby the camera 12 is also referred to as a visible light image; the imagein the wavelength range of 1166±5 nm, an infrared image A; the image inthe wavelength range of 1190±5 nm, an infrared image B; and the image inthe wavelength range of 1214±5 nm, an infrared image C.

The structure of the camera 12 is described here. The camera 12comprises, as shown in FIG. 3 , a lens 121, a beam splitter 122, filters123 (123 _(A) to 123 _(D)) provided corresponding to the above-describedwavelength ranges, and complementary metal oxide semiconductor devices(CMOSs) 124 (124 _(A) to 124 _(D)).

The lens 121 collects the incident light. The beam splitter 122 is, forexample, a prism or one way mirror and splits the light collected by thelens 121. The filters 123 transmit light in the corresponding wavelengthranges in the light split by the beam splitter 122. Specifically, thefilters 123 _(A) to 123 _(D) transmit light in the wavelength range of1166±5 nm, in the wavelength range of 1190±5 nm, in the wavelength rangeof 1214±5 nm, and in the visible light range, respectively.

Moreover, the CMOSs 124 _(A) to 124 _(D) provided corresponding to thefilters 123 _(A) to 123 _(D) convert light transmitted through thefilters 123 _(A) to 123 _(D) to electric signals to create images in thecorresponding wavelength ranges. Specifically, the CMOSs 124 _(A) to 124_(D) create infrared images A to C and a visible light image,respectively. Here, image sensors such as charge-coupled devices (CCDs)may be used in place of the CMOSs 124.

Returning to FIG. 2 , the speaker 13 outputs sound based on control ofthe controller 17. The liquid crystal monitor 14 displays various kindsof information based on control of the controller 17. For example, whenit is detected that a person is wearing a disguising mask, thecontroller 17 controls the speaker 13 to output a warning sound forgiving notice accordingly and the liquid crystal monitor 14 to display awarning message.

The operator 15 comprises various buttons and when the user conduct anoperation, outputs a signal corresponding to the operation to thecontroller 17.

The external storage 16 is, for example, a hard disc drive or the like,and serves as a temporal storage of images captured by the camera 12 andstores various data necessary for the mask detection procedure describedlater.

The controller 17 is configured by a central processing unit (CPU), aread only memory (ROM), a random access memory (RAM), and the like, andcontrols the entire disguising mask detecting device 1. The controlprocedure of the controller 17 is executed by, specifically, the CPUexecuting control programs stored in the ROM while using the RAM as thework area to temporarily store various data. The controller 17functionally comprises an imaging controller 171, a face detector 172, adeterminer 173, and a notifier 174.

The imaging controller 171 controls turning-on/turning-off of the lightsource 11 and imaging operation of the camera 12 so as to acquire imagesof a person in the wavelength ranges (a visible light image and infraredimages A to C).

The face detector 172 analyzes the visible light image captured by thecamera 12 and detects a face region of the person. Then, the facedetector 172 detects in the face region a forehead region, a right cheekregion, and a left cheek region, which are situated near facecharacteristic quantities (eyes, nose, mouth, and the like) and wherethe skin is exposed in a relatively large area.

Here, the camera 12 captures the images of a person (a visible lightimage and infrared images A to C) all at once from the same point and atthe same time. Therefore, the regions in the visible light imagedetected by the face detector 172 share the pixel positions with theregions in the other images (infrared images A to C) captured at thesame time.

Here, a known detection method can be used for the face detector 172 todetect the regions.

For example, the face detector 172 applies the Sobel filter to thevisible light image to detect outlines and extracts a face outline byface outline pattern matching. Then, the face detector 172 detectseyebrow outlines from above and an outline under the mouth from belowwithin the extracted face outline and detects as a face region a regionsurrounded by the right and left ends of the face and the positionsabove the eyebrows and under the mouth. Then, the face detector 172detects the black points corresponding to the eyeballs in the detectedface region as the eye positions and specifies a forehead region, aright cheek region, and a left cheek region from the face region and eyepositions based on general face statistical data. Here, the facedetector 172 may detect face characteristic quantities such as the eyes,nose, and mouth by a known technique and when those characteristicquantities are detected, specify their neighboring regions as a foreheadregion, a right cheek region, and a left cheek region.

Here, the above-described processing by the face detector 172 will bedescribed using a specific example. For example, it is assumed that avisible light image as shown in FIG. 4A is given as the processingtarget of the face detector 172. In such a case, the face detector 172detects a face region R1 as shown in FIG. 4B. Moreover, the facedetector 172 detects a forehead region R2, a right cheek region R3, anda left cheek region R4 from the face region R1.

Returning to FIG. 2 , the determiner 173 judges whether the luminancesof the regions (the forehead region, right cheek region, and left cheekregion) specified by the face detector 172 satisfy specific relationsbetween the infrared images A to C that are different from relationsexhibited by skin so as to judge whether there is an abrupt fall in thewavelength range marked by the hatched lines in FIG. 1 and determinewhether the person is wearing a disguising mask.

When the determiner 173 determines that a disguising mask is worn, thenotifier 174 controls the speaker 13 and liquid crystal monitor 14 togive notice accordingly.

Subsequently, the disguising mask detection procedure executed by thedisguising mask detecting device 1 will be described. An immigrationofficer guides a person entering the country into the field angle of thecamera 12 of the disguising mask detecting device 1 installed near anentry gate. In doing so, the officer conducts an operation to start theprocessing via the operator 15 of the mask detecting device 1. Inresponse to the operation, the controller 17 of the mask detectingdevice executes the mask detection procedure shown in the flowchart ofFIG. 5 .

Here, the disguising mask detecting device 1 may comprise a motionsensor and when the motion sensor detects a person entering the country,execute the mask detection procedure. Alternatively, with the camera 12set in the live view mode, the mask detection procedure may be executedautomatically when the controller 17 determines that a person is oncamera.

Moreover, a person wearing a disguising mask may become cautious when hesees the lens of the camera 12 or the like. Therefore, for example, amagic mirror may be placed in front of the camera 12 so that the maskdetection procedure starts with an image captured unnoticeably.

In the mask detection procedure of FIG. 5 , first, the imagingcontroller 171 turns on the light source 11 and controls the camera 12to acquire images of the person in the wavelength ranges (a visiblelight image and infrared images A to C) (Step S11).

Subsequently, the face detector 172 detects a face region from theacquired visible light image and detects a forehead region, a rightcheek region, and a left cheek region from the face region (Step S12).

Subsequently, the determiner 173 compares the luminances of the regions(forehead region, right cheek region, and left cheek region) in theinfrared images A to C acquired at the same time as the visible lightimage in the Step S11 so as to execute the mask determination procedureto determine whether the person is wearing a disguising mask (Step S13).

Here, details of the mask determination procedure will be described withreference to the flowchart of FIG. 6 .

First, the determiner 173 selects one of the regions unselected in theongoing mask determination procedure from among the detected foreheadregion, right cheek region, and left cheek region (Step S131). Theregion selected in the Step S131 is also referred to as the selectedregion hereafter.

Subsequently, the determiner 173 selects one pixel from the selectedregion (for example, the pixel at the center of the selected region) andmeasures the luminance of the pixel in each of the infrared images A toC (Step S132).

Subsequently, the determiner 173 judges whether the measured luminancessatisfy specific relations between the infrared images A to C (StepS133). Specifically, the determiner 173 judges the luminance measured inthe infrared image B is lower than the luminances measured in theinfrared image A and infrared image C by a given rate. As a result, itis possible to judge whether there is an abrupt fall in luminance ofreflected light in the silicone-specific wavelength range (thewavelength range around 1140 nm to 1220 nm shown in FIG. 1 ) that is notobserved with human skin.

Here, more specifically, the determiner 173 has only to judge whetherthe following relational expressions (1) to (3) are all satisfied in theStep S133. Here, in the relational expressions (1) to (3), IA is theluminance measured in the infrared image A, IB is the luminance measuredin the infrared image B, and IC is the luminance measured in theinfrared image A. Moreover, T1 to T3 are coefficients and preset tonumerical values optimum for the mask detection based on image capturingconditions.

IA×T1>IB  (1)

IC×T2>IB  (2)

IC×T3>IA  (3)

If the above relational expressions (1) and (2) are satisfied, theluminance measured in the infrared image B is lower than the luminancesmeasured in the infrared image A and infrared image C by a given rate.Moreover, if the above relational expression (3) is satisfied, theluminance measured in the infrared image C is higher than the luminancemeasured in the infrared image A by a given rate.

If the measured luminances satisfy the specific relations (Step S133;Yes), the determiner 173 measures, in each of the infrared images A toC, the luminances of eight pixels surrounding the pixel measured in theStep S132 (Step S134).

Subsequently, the determiner 173 judges whether the measured luminancesof the surrounding pixels also satisfy the specific relations betweenthe infrared images A to C (Step S135).

If the luminances of the surrounding pixels also satisfy the specificrelations (Step S135; Yes), the determiner 173 determines that theperson is wearing a disguising mask (Step S136) and the maskdetermination procedure ends. Here, in the above-described maskdetermination procedure, it is determined that a disguising mask is wornwhen one pixel and eight pixels surrounding that pixel in any one of theselected regions (forehead, right cheek, and left cheek) all satisfy thespecific relations. This is because a disguising mask is generally wornto cover the entire face and if an abrupt fall in luminance in thespecific wavelength range is observed in any one of the selectedregions, it is possible to determine that a disguising mask is wornwithout executing the mask determination procedure on the other selectedregions.

On the other hand, if the luminance of one pixel in the selected regiondoes not satisfy the specific relations (Step S133; No) or theluminances of the surrounding pixels do not satisfy the specificrelations (Step S135; No), the determiner 173 judges whether all of theforehead region, right cheek region, and left cheek region are selectedin the ongoing mask determination procedure (Step S137).

If not all of the forehead region, right cheek region, and left cheekregion are selected (Step S137; No), the processing returns to the StepS131 and the determiner 173 selects an unselected region and repeats aseries of processing to judge whether the luminances of pixels in thatregion satisfy the specific relations so as to determine whether adisguising mask is worn.

On the other hand, if all of the forehead region, right cheek region,and left cheek region are selected (Step S137; Yes), the determiner 173determines that the person is not wearing a disguising mask (Step S138)and the mask determination procedure ends.

Returning to FIG. 5 , after the mask determination procedure (Step S13)ends, the notifier 174 judges whether it is determined in the maskdetermination procedure that a disguising mask is worn (Step S14). If adisguising mask is not worn (Step S14; Yes), the disguising maskdetection procedure ends.

On the other hand, if a disguising mask is worn (Step S14; Yes), thenotifier 174 controls the speaker 13 and liquid crystal monitor 14 togive notice accordingly (Step S15). As a result, the officer can noticethe disguise of the person trying to pass through the entry gate,thereby preventing illegal entry. Then, the disguising mask detectionprocedure ends.

As described above, the disguising mask detecting device 1 according toEmbodiment 1 acquires (captures) images of a person in multipledifferent wavelength ranges and when the luminances of the face regionsatisfy specific relations between the acquired images that aredifferent from relations exhibited by skin, judges that the person iswearing a disguising mask. In other words, the disguising mask detectingdevice 1 according to Embodiment 1 judges that a person is wearing adisguising mask when a concave shape is formed by connecting theluminances of the face region in the acquired images. As a result,highly accurate detection of a disguising mask with the use of thedifference in spectrum of luminance of reflected light between siliconeand human skin is made possible.

Moreover, the disguising mask detecting device 1 according to Embodiment1 detects characteristic regions where the skin is exposed in arelatively large area (forehead region, right cheek region, and leftcheek region) from the face region in the acquired images and detects adisguising mask using the luminances of the characteristic regions.Therefore, the mask determination procedure does not need to be executedon the entire face region, whereby the mask detection processing load isreduced.

Moreover, the disguising mask detecting device 1 according to Embodiment1 judges whether a disguising mask is worn using not only the luminanceof one pixel but also the luminances of pixels surrounding that pixel.Therefore, more accurate detection of a disguising mask is madepossible.

Moreover, the disguising mask detecting device 1 according to Embodiment1 detects the presence/absence of a disguising mask with a camera usingimages in four different wavelength ranges (a visible light image andinfrared images A to C), whereby detection of a disguising mask with arelatively small load is made possible.

Moreover, the light source 11 of the disguising mask detecting device 1according to Embodiment 1 is a halogen light source and therefore asufficient amount of light in the infrared band can be obtained.Therefore, highly accurate detection of a disguising mask is madepossible.

Embodiment 2

Subsequently, a disguising mask detecting device 2 according toEmbodiment 2 will be described. Here, as shown in FIG. 3 , thedisguising mask detecting device 2 is substantially the same inconfiguration of components as the disguising mask detecting device 1according to Embodiment 1 and different only in the contents of the maskdetermination procedure.

The mask determination procedure executed by the mask detecting device 2will be described using the flowchart of FIG. 7 . Here, as for the stepsof which the contents are substantially the same as in the maskdetermination procedure shown in FIG. 6 , their explanation will besimplified as appropriate. Moreover, the timing of starting the maskdetermination procedure in FIG. 7 is the same as in FIG. 6 .

As the mask determination procedure starts, first, the determiner 173selects an unselected region from among the detected forehead region,right cheek region, and left cheek region (Step S201), selects one pixelin the selected region and measures the luminance of the pixel in eachof the infrared images A to C (Step S202), and judges whether themeasured luminances satisfy the specific relations between the infraredimages A to C (Step S203).

If the luminances do not satisfy the specific relations between theinfrared images A to C (Step S203; No), the determiner 173 calculates amask determination score of the selected region to be zero (Step S204)and the processing advances to Step S206.

On the other hand, if the luminances satisfy the specific relationsbetween the infrared images A to C (Step S203; Yes), the determiner 173measures, in each of the infrared images A to C, the luminances ofpixels surrounding the pixel measured in the Step S202 (for example,eight pixels neighboring the measured pixel). Then, the determiner 173calculates the rate at which the luminances of the surrounding pixelssatisfy the specific relations between the infrared images A to C as ascore of the selected region (Step S205), and the processing advances tothe Step S206. For example, if the luminances of all eight surroundingpixels satisfy the specific relations between the infrared images A toC, the score is calculated to be 1 (8/8). On the other hand, if theluminances of two of the eight surrounding pixels satisfy the specificrelations between the infrared images A to C, the score is calculated tobe 0.25 (2/8).

In the Step S206, the determiner 173 judges whether all of the foreheadregion, right cheek region, and left cheek region are selected. If notall of the forehead region, right cheek region, and left cheek regionare selected (Step S206; No), the processing returns to the Step S201.

If all of the forehead region, right cheek region, and left cheek regionare selected (Step S206; Yes), the determiner 173 calculates the averageof the scores calculated for the regions as the final score (Step S207).Then, the determiner 173 judges whether the final score is equal to orhigher than a given threshold (for example, 0.5) (Step S208).

If the final score is equal to or higher than the threshold (Step S208;Yes), the determiner 173 determines that the person is wearing adisguising mask (Step S209). On the other hand, if the final score islower than the threshold (Step S208; No), the determiner determines thatthe person is not wearing a disguising mask (Step S210). Then, the maskdetermination procedure ends.

As described above, in the mask determination procedure of Embodiment 2,a disguising mask determination score is calculated for each of theright cheek region, left cheek region, and forehead region and it isdetermined whether a disguising mask is worn. Therefore, it is possibleto detect a disguising mask with higher accuracy than the maskdetermination procedure of Embodiment 1 in which it is immediatelydetermined that a disguising mask is worn when the luminances of any oneof the regions (cheek region, right cheek region, and left cheek region)satisfy the specific relations.

Embodiment 3

Subsequently, a disguising mask detecting device 3 according toEmbodiment 3 will be described. Here, as shown in FIG. 3 , thedisguising mask detecting device 3 is substantially the same inconfiguration of components as the disguising mask detecting devices 1and 2 according to Embodiments 1 and 2 and different only in thecontents of the mask determination procedure.

The mask determination procedure executed by the mask detecting device 3will be described using the flowchart of FIG. 8 . Here, as for the stepsof which the contents are substantially the same as in the maskdetermination procedure shown in FIG. 6 , their explanation will besimplified as appropriate. Moreover, the timing of starting the maskdetermination procedure in FIG. 8 is the same as in FIG. 6 .

As the mask determination procedure starts, first, the determiner 173initializes a possible silicone counter and non-silicone counter used indisguising mask determination to zero (Step S301).

Subsequently, the determiner 173 selects one of the forehead region,right cheek region, and left cheek region (Step S302). Then, thedeterminer 173 selects one of the unselected pixels in the selectedregion (Step S303). The pixel selected in the Step S303 is also referredto as the selected pixel hereafter.

Subsequently, the determiner 173 measures the luminance of the selectedpixel in each of the infrared images A to C (Step S304). Then, thedeterminer 173 judges whether the measured luminances satisfy thespecific relations between the infrared images A to C (Step S305).

If the measured luminances satisfy the specific relations (Step S305;Yes), the determiner adds one to the possible silicone counter (StepS306). On the other hand, if the measured luminances do not satisfy thespecific relations (Step S305; No), the determiner adds one to thenon-silicone counter (Step S307).

Subsequently, the determiner 173 determines whether all pixels in theselected region are selected (Step S308).

If not all pixels are selected (Step S308; No), the processing returnsto the Step S303 and the determiner 173 selects one pixel from theselected region and repeats the process to add one to the non-siliconecounter or to the possible silicone counter based on the luminances ofthe pixel.

On the other hand, if all pixels are selected (Step S308; Yes), thedeterminer 173 judges whether all of the forehead region, right cheekregion, and left cheek region are selected (Step S309). If not all ofthe forehead region, right cheek region, and left cheek region areselected (Step S309; No), the processing returns to the Step S302.

If all of the forehead region, right cheek region, and left cheek regionare selected (Step S309; Yes), in other words after the possiblesilicone counter or non-silicone counter is incremented for each of allpixels in the forehead region, right cheek region, and left cheekregion, the determiner 173 judges whether the possible silicone counterhas a higher value than the non-silicone counter (Step S310).

If the possible silicone counter has a higher value than thenon-silicone counter (Step S310; Yes), the determiner 173 determinesthat the person is wearing a disguising mask (Step S311).

On the other hand, if the possible silicone counter does not have ahigher value than the non-silicone counter (Step S310; No), thedeterminer 173 determines that the person is not wearing a disguisingmask (Step S312). Then, the disguising mask determination procedureends.

As described above, in the mask determination procedure of Embodiment 3,all pixels in the forehead region, right cheek region, and left cheekregion are used to determine a disguising mask, whereby it is possibleto detect a disguising mask with higher accuracy.

Here, in the mask detection procedure of FIG. 8 , it may be possible touse only the possible silicone counter and detect a mask based onwhether the possible silicone counter has a value equal to or higherthan a given value in the Step S310. For example, with the given valueset to 80% of all pixels in the forehead region, right cheek region, andleft cheek region, it is possible to judge that a mask is worn when 80%or more of all pixels are of possible silicone.

Moreover, in the mask detection procedure of FIG. 8 , the possiblesilicone counter is increased by one in the Step S306 when theluminances of the selected pixel satisfy the specific relations (StepS305; Yes). However, it may be possible that when the luminances of theselected pixel satisfy the specific relations, it is determined as inEmbodiment 1 whether the surrounding pixels satisfy the specificrelations and only if satisfying, the possible silicone counter isincreased by one.

Modified Embodiments

The present disclosure is not confined to the above embodiments andneedless to say, various changes can be made to the extent of notdeparting from the gist of the present disclosure.

For example, the disguising mask detecting devices 1 to 3 according tothe above-described embodiments eventually detect a disguising mask.However, the present disclosure is applicable to a detecting devicedetecting a thing to disguise attached to the skin, which is notnecessarily a disguising mask.

Moreover, in the disguising mask detecting devices 1 to 3 according tothe above-described embodiments, the determiner 173 determines whether aperson is wearing a disguising mask in the mask determination procedure.However, it may be possible that without the determination itself as towhether a disguising mask is worn, the determiner 173 determines onlywhether the luminances satisfy the specific relations between theinfrared images and if satisfying, the notifier 174 gives noticeaccordingly.

Moreover, the disguising mask detecting devices 1 to 3 shown in FIG. 2are described on the assumption that the light source 11, camera 12, andthe like are all integrated. Needless to say, they may be separated asappropriate. For example, the light source 11, camera 12, speaker 13,and the like may be separately prepared and combined with a devicehaving the function of the controller 17 (for example, a PC or the like)to configure the disguising mask detecting devices 1 to 3.Alternatively, it may be possible that the function of the controller 17is built in the camera 12 and the controller of the camera 12 workstogether with the light source 11, speaker 13, and the like asappropriate to configure the disguising mask detecting device 1.

Moreover, in the above-described embodiments, it is determined that adisguising mask is worn when the luminances of an image in a wavelengthrange of 1166±5 nm (infrared image A), an image in a wavelength range of1190±5 nm (infrared image B), and an image in a wavelength range of1214±5 nm (infrared image C) satisfy the specific relations. However,the presence/absence of a disguising mask may be determined using imagesin other wavelength ranges as long as change in luminance of reflectedlight different from human skin can be detected. For example, obviousdifference in spectrum of luminance of reflected light between siliconeand human skin is observed in a wavelength range around 1500 nm to 1550nm marked by a shaded area in FIG. 1 . Therefore, it may be possible toprepare multiple filters for the wavelength range in the shaded area,acquire multiple images of a person, and determine the presence/absenceof a disguising mask from the luminances of the face region. Moreover,images in the wavelength ranges both in the hatched area and in theshaded area may be used in the mask detection procedure and in such acase, the accuracy of detecting a mask can be improved.

Moreover, in the above-described embodiments, the luminances of imagesin three wavelength ranges (infrared images A to C) are used todetermine the presence/absence of a disguising mask. The luminances ofimages in three or more wavelength ranges may be used to determine thepresence/absence of a disguising mask.

Moreover, in the above-described embodiments, the face detector 172detects a forehead region, a right cheek region, and a left cheek regionfrom the face region, and the determiner 173 compares the luminances ofthe regions in the images to determine the presence/absence of adisguising mask. However, the face detector 172 does not need to detectall of a forehead region, right cheek region, and left cheek region, andhas only to detect at least one region. For example, it may be possiblethat the face detector 172 detects only a forehead region and thedeterminer 173 compares only the luminances of the forehead region todetermine the presence/absence of a disguising mask. Moreover, it may bepossible that the face detector 172 detects a characteristic regionother than the forehead region, right cheek region, and left cheekregion and the luminances of that region are used to determine thepresence/absence of a disguising mask. Moreover, it may be possible thatthe face detector 172 detects only a face region and the determiner 173compares the luminances of the entire face region or a part thereof todetermine the presence/absence of a disguising mask.

Moreover, when the positions of the camera 12 and 13 and the point ofphotographing a person are fixed so that the face of the persondefinitely appears in a specific area of the image, the determiner 173may compare the luminances of that specific area to determine thepresence/absence of a disguising mask. In such a case, the disguisingmask detecting devices 1 to 3 do not need to comprise the face detector171.

Moreover, in the above-described embodiments, as shown in FIG. 3 , thecamera 12 of the disguising mask detecting device 1 comprises the beamsplitter 122 and multiple filters 123, whereby multiple images indifferent wavelength ranges can be captured at a time.

However, the present disclosure is applicable even to a disguising maskdetecting device 1′ comprising, as shown in FIG. 9 , four cameras 18 (18_(A) to 18 _(D)) capturing only an image in a single wavelength range inplace of such a camera 12. Here, the cameras 18 _(A) to 18 _(D) eachcomprise a filter allowing light only in a wavelength range of 1166±5nm, in a wavelength range of 1190±5 nm, in a wavelength range of 1214±5nm, and in the visible light range, respectively, to transmit throughthe CMOS. Therefore, the cameras 18 _(A) to 18 _(D) can capture onlyinfrared images A to D and a visible light image, respectively.

Here, the external storage 16 of the disguising mask detecting device 1′stores position parameters presenting the positional relations of thecameras 18 _(A) to 18 _(D). The position parameters are informationpresenting, for example, the relative position coordinates (x, y, z),vertical angle (tilt), horizontal angle (pan), rotational angle (roll),and the like of the cameras 18 _(A) to 18 _(D).

In the disguising mask detecting device 1′, as shown in FIG. 9 , theangles of reflected light from the person are different; therefore, theimages in the wavelength ranges are not those captured at one and thesame point. Then, when the luminances of a selected pixel in theinfrared images A to C are measured in the mask determination procedure,the position of the pixel is not the same.

Therefore, in the disguising mask detecting device 1′, the controller 17comprises an image corrector 175 acquiring images in which the imagescaptured by the multiple cameras 18 _(A) to 18 _(D) are corrected as ifthe person was photographed at one and the same point.

For example, using a known technique, the image corrector 175angularly-corrects the images captured at the positions of the cameras18B to 18 _(D) so that they are at the same position as the imagecaptured at the position of the camera 18 _(A) with reference to theposition parameters stored in the external storage 16. As a result,images sharing the pixel positions can be obtained. Then, the facedetector 172 and determiner 173 can execute the mask detection procedureon the sharing images obtained by the image corrector 175.

The disguising mask detecting device 1′ allows for use of camerassimpler in structure than the camera 12 of the disguising mask detectingdevice 1 using the beam splitter 122 and multiple filters 123 _(A) to123 _(D), whereby the disguising mask detecting device 1′ caninexpensively be configured.

Moreover, the above-described embodiments are described using a case ofdetecting a disguising mask. Skin may be detected along with detectionof a disguising mask. In such a case, relational expressions fordetecting skin are obtained in advance and it is determined whether itis skin with the obtained relational expressions along withdetermination of whether the luminances of a selected pixel in theinfrared images A to C satisfy the specific relations, whereby it ispossible to detect whether the pixel is of silicone or of skin.Therefore, it is possible to determine whether a disguising mask is wornwith higher accuracy.

Moreover, in the disguising mask detecting devices 1 to 3 in theabove-described embodiments, the filters 123 _(A) to 123 _(D) that arebandpass filters transmitting light in the wavelength ranges are used.This is not restrictive and other filters may be used. Images in desiredwavelength ranges may be obtained by, for example, using a cutoff filtercutting off all infrared light in order to obtain a visible light imageor combining multiple filters in order to obtain images in multipledifferent wavelength ranges in the infrared band (for example, combininga cutoff filter cutting off light of 1160 nm or shorter and a cutofffilter cutting off light of 1172 nm or longer in order to obtain animage in a wavelength range of 1166±5 nm).

Moreover, the above-described embodiments are described using a case ofinstalling the disguising mask detecting devices 1 to 3 in animmigration area. The place where the disguising mask detecting devices1 to 3 are installed is not restricted to this. The bottom line is, thedisguising mask detecting device 1 can be installed to detect adisguising mask where a disguising mask has to be detected. For example,the disguising mask detecting devices 1 to 3 may be installed for usenear, evidently, a departure gate in an immigration area or at anentrance to a company or large-scale leisure facility.

Moreover, in the above-described embodiments, the disguising maskdetecting devices 1 to 3 detect a silicone disguising mask. The presentdisclosure can be used for detecting a disguising mask made of someother material. In such a case, it is necessary to acquire multipleimages in wavelength ranges in which the spectrum of luminance ofreflected light is largely different between the disguising maskmaterial and human skin.

For example, a resin mask exhibits high luminance in a wavelength rangeof 1480 to 1580 nm while human skin exhibits low luminance in thiswavelength range. Moreover, a synthetic rubber mask exhibits extremelylower luminance in a wavelength range of 1480 to 1580 nm than humanskin. Therefore, taking into account such difference between the skinand other material, it is possible to detect a resin or synthetic rubbermask.

Moreover, it is possible to apply operation programs defining theoperation of the disguising mask detecting devices 1 to 3 according tothe above-described embodiments to an existing personal computer,information terminal device, or the like to allow the personal computeror the like to function as the disguising mask detecting devices 1 to 3according to the present disclosure.

Moreover, such programs are distributed by any method and, for example,may be saved and distributed on a non-transitory computer-readablerecording medium such as a compact disk read only memory (CD-ROM),digital versatile disk (DVD), magneto-optical disk (MO), and memory cardor distributed via a communication network such as the Internet.

The foregoing describes some example embodiments for explanatorypurposes. Although the foregoing discussion has presented specificembodiments, persons skilled in the art will recognize that changes maybe made in form and detail without departing from the broader spirit andscope of the invention. Accordingly, the specification and drawings areto be regarded in an illustrative rather than a restrictive sense. Thisdetailed description, therefore, is not to be taken in a limiting sense,and the scope of the invention is defined only by the included claims,along with the full range of equivalents to which such claims areentitled.

The above-described embodiments are entirely or partly, but notexclusively, described as in the following Supplementary Notes.

(Supplementary Note 1)

A detecting device, comprising:

-   -   an image acquirer acquiring images in multiple different        wavelength ranges of reflected light of light emitted at a        person; and    -   a determiner determining whether luminances of a face region in        the images acquired by the image acquirer satisfy specific        relations different from relations exhibited by skin.

(Supplementary Note 2)

The detecting device according to Supplementary Note 1, wherein

-   -   the determiner determines that the person is wearing a disguise        when the specific relations are satisfied.

(Supplementary Note 3)

The detecting device according to Supplementary Note 1 or 2, wherein

-   -   the image acquirer acquires multiple images in different        wavelength ranges within an infrared band, and    -   the determiner determines that the specific relations are        satisfied when a waveform presented by distribution of the        luminances of the face region in the images is concave.

(Supplementary Note 4)

The detecting device according to any one of Supplementary Notes 1 to 3,wherein

-   -   the image acquirer acquires images in wavelength ranges around        1166 nm, around 1190 nm, and around 1214 nm separately, and    -   the determiner determines that the specific relations are        satisfied when the luminance of the face region in the image in        the wavelength range around 1190 nm is lower than the luminances        of the face region in the images in the wavelength ranges around        1166 nm and around 1214 nm by a given rate.

(Supplementary Note 5)

The detecting device according to any one of Supplementary Notes 1 to 3,wherein

-   -   the image acquirer acquires images in wavelength ranges around        1166 nm, around 1190 nm, and around 1214 nm, and    -   the determiner determines that the specific relations are        satisfied when the luminance of the face region in the image in        the wavelength range around 1190 nm is lower than the luminances        of the face region in the images in the wavelength ranges around        1166 nm and around 1214 nm by a given rate and the luminance        within the face region in the image in the wavelength range        around 1214 nm is higher than the luminance of the face region        in the image in the wavelength range around 1166 nm by a given        rate.

(Supplementary Note 6)

The detecting device according to any one of Supplementary Notes 1 to 5,comprising:

-   -   a face detector detecting a face region of the person from the        images acquired by the image acquirer,    -   wherein the determiner determines whether the luminances of the        face region detected by the face detector satisfy the specific        relations.

(Supplementary Note 7)

The detecting device according to Supplementary Note 6, wherein

-   -   the face detector detects a characteristic region from the face        region, and    -   the determiner determines whether the luminances of the        characteristic region in the images detected by the face        detector satisfy specific relations.

(Supplementary Note 8)

The detecting device according to Supplementary Note 7, wherein

-   -   the face detector detects at least one of a forehead region,        right cheek region, and left cheek region as the characteristic        region.

(Supplementary Note 9)

The detecting device according to any one of Supplementary Notes 1 to 8,wherein

-   -   the image acquirer acquires the images in multiple different        wavelength ranges by splitting reflected light of the light        emitted at the person.

(Supplementary Note 10)

The detecting device according to any one of Supplementary Notes 1 to 8,wherein

-   -   the image acquirer comprises:    -   multiple image capturers provided at different positions for        each of the specific wavelength ranges and capturing images in        corresponding wavelength ranges; and    -   an image corrector acquiring images in which the images captured        by the multiple image capturers are corrected as if the person        was photographed at one and the same point.

(Supplementary Note 11)

The detecting device according to any one of Supplementary Notes 1 to10, wherein

-   -   the determiner further comprises a notifier giving notice of the        specific relations being satisfied when determined so.

(Supplementary Note 12)

The detecting device according to any one of Supplementary Notes 1 to11, wherein

-   -   the light emitted at the person is infrared light emitted from a        halogen light source.

(Supplementary Note 13)

The detecting device according to Supplementary Note 2, wherein

-   -   the disguise is a disguise with a silicone disguising mask.

(Supplementary Note 14)

A detecting method, comprising:

-   -   an image acquisition step of acquiring images in multiple        different wavelength ranges of reflected light of light emitted        at a person; and    -   a determination step of determining whether luminances of a face        region in the images acquired in the image acquisition step        satisfy specific relations different from relations exhibited by        skin.

(Supplementary Note 15)

A non-transitory recording medium saving a program that allows acomputer to function as:

-   -   a determiner determining whether luminances of a face region in        images of a person captured in multiple different wavelength        ranges satisfy specific relations different from relations        exhibited by skin.

INDUSTRIAL APPLICABILITY

The present disclosure is preferably used for determining whether aperson entering a country is disguising in an immigration area.

REFERENCE SIGNS LIST

-   -   1, 2, 3, 1′ Disguising mask detecting device    -   11 Light source    -   12, 18 (18 _(A) to 18 _(D)) Camera    -   121 Lens    -   122 Beam splitter    -   123 (123 _(A) to 123 _(D)) Filter    -   124 (124 _(A) to 124 _(D)) CMOS    -   13 Speaker    -   14 Liquid crystal monitor    -   Operator    -   16 External storage    -   17 Controller    -   171 Imaging controller    -   172 Face detector    -   173 Determiner    -   174 Notifier    -   175 Image corrector

1. A detecting device comprising: at least one memory configured tostore instructions; and at least one processor configured to execute theinstructions to perform: acquiring a visible light image including aface region of a person; acquiring a first infrared light image in afirst infrared wavelength range, a second infrared light image in asecond infrared wavelength range longer than the first infraredwavelength range and a third infrared light image in a third infraredwavelength range longer than the second infrared wavelength range,wherein a wavelength range between the first infrared wavelength rangeand the third infrared wavelength range is the wavelength range in whichan inclination of change in luminance of reflected light on a siliconmask is different from an inclination of change in luminance ofreflected light on a human skin; detecting the face region of the personin the visible light image; and when a difference between luminance ofthe first infrared light image and luminance of the second infraredlight image, and a difference between the luminance of the secondinfrared light image and luminance of the third infrared light imagewith respect to at least one part of the face region of the personsatisfy specific relations, giving notice accordingly.
 2. The detectingdevice according to claim 1, wherein the at least one processor isconfigured to execute the instructions to perform: determining that theperson is disguised when the inclination of change in luminance of theinfrared light reflected from the face region has a concave shapewaveform.
 3. The detecting device according to claim 1, wherein the atleast one processor is configured to execute the instructions toperform: determining that the person is disguised when concave shape ofa waveform of the inclination of change in luminance of the infraredlight reflected from the at least one part of the face region is moreconcave than a predetermined amount.
 4. A detecting method comprising:acquiring a visible light image including a face region of a person;acquiring a first infrared light image in a first infrared wavelengthrange, a second infrared light image in a second infrared wavelengthrange longer than the first infrared wavelength range and a thirdinfrared light image in a third infrared wavelength range longer thanthe second infrared wavelength range, wherein a wavelength range betweenthe first infrared wavelength range and the third infrared wavelengthrange is the wavelength range in which an inclination of change inluminance of reflected light on a silicon mask is different from aninclination of change in luminance of reflected light on a human skin;detecting the face region of the person in the visible light image; andwhen a difference between luminance of the first infrared light imageand luminance of the second infrared light image, and a differencebetween the luminance of the second infrared light image and luminanceof the third infrared light image with respect to at least one part ofthe face region of the person satisfy specific relations, giving noticeaccordingly.
 5. The detecting method according to claim 4, wherein thedetecting method comprises: determining that the person is disguisedwhen the inclination of change in luminance of the infrared lightreflected from the face region has a concave shape waveform.
 6. Thedetecting method according to claim 4, wherein the detecting methodcomprises: determining that the person is disguised when concave shapeof a waveform of the inclination of change in luminance of the infraredlight reflected from the at least one part of the face region is moreconcave than a predetermined amount.
 7. A non-transitory programrecording medium that records a program causing a computer to executeprocessing of: acquiring a visible light image including a face regionof a person; acquiring a first infrared light image in a first infraredwavelength range, a second infrared light image in a second infraredwavelength range longer than the first infrared wavelength range and athird infrared light image in a third infrared wavelength range longerthan the second infrared wavelength range, wherein a wavelength rangebetween the first infrared wavelength range and the third infraredwavelength range is the wavelength range in which an inclination ofchange in luminance of reflected light on a silicon mask is differentfrom an inclination of change in luminance of reflected light on a humanskin; detecting the face region of the person in the visible lightimage; and when a difference between luminance of the first infraredlight image and luminance of the second infrared light image, and adifference between the luminance of the second infrared light image andluminance of the third infrared light image with respect to at least onepart of the face region of the person satisfy specific relations, givingnotice accordingly.
 8. The non-transitory program recording mediumaccording to claim 7, wherein the program causes the computer to executeprocessing of: determining that the person is disguised when theinclination of change in luminance of the infrared light reflected fromthe face region has a concave shape waveform.
 9. The non-transitoryprogram recording medium according to claim 7, wherein the programcauses the computer to execute processing of: determining that theperson is disguised when concave shape of a waveform of the inclinationof change in luminance of the infrared light reflected from the at leastone part of the face region is more concave than a predetermined amount.